CFD Analysis On Rotation Flow Field Of CQQ-01 Vacuum Degasser And Parameters Optimization Of Impeller

Strictly controlling the performance parameters of drilling fluid is of great significance for pressure-balanced drilling.The phenomenon of gas cutting can seriously change the density of drilling fluid.As a result,the density of drilling fluid decreases and the viscosity increases.It can do great harm to the drilling safety.The degasser is a device that used to remove small bubbles of gas-cut drilling fluid.The vacuum degasser has been widely used because of its simple structure,large capacity and high efficiency.In order to achieve the requirement of gas removal efficiency,the performance of the vacuum degasser is analyzed.And the performance of the degasser is largely determined by the distribution of its internal rotation flow field.In this paper,CQQ-01 vacuum degasser is used as the research object.CFD method is used to analyze the internal rotation flow field of the degasser.The impeller's structure parameters and operation parameters impact on the flow field are also analyzed.Therefore,the result provides the basis for selecting the impeller's parameters reasonably.In this paper,the Inventor software is used to set up the three dimensional model of the degasser.The CFD simulation model of the rotary zone of the degasser is established by using the CFD analysis software STAR-CCM +.Then,the simulation model is numerically calculated.The residual monitoring curve,inlet pressure monitoring curve and outlet flowrate monitoring curve of the calculated results show that the calculation accuracy of the model is up to the requirements.The velocity field,pressure field of the intermediate section of rotary zone of the degasser,and the pressure field of the blade working face and the blade back face are analyzed.The result show that: From the blade inlet to the outlet of the blade,due to the rotation of the blade,the fluid velocity increases gradually and the pressure increases gradually;From the outlet of the blade to the outlet of the diffuser,the fluid velocity decreases gradually and the pressure increases gradually,and the kinetic energy loss caused by the decrease of fluid velocity is converted into the pressure energy of the liquid;Local backflow and vortex occur in the area near the inner wall of the diffuser,resulting in a low velocity of the inner wall area;The flow direction of liquid in other areas of the diffuser is basically parallel to the outer wall,and finally perpendicular to the outlet;The pressure on the blade working face and back face both increases with the diameter,but on the circumference of the same diameter,the pressure of the working face is higher than the back face.Based on the analysis of CFD calculation results and the working principle of centrifugal impeller machine,the correctness of CFD model is verified.In order to obtain the reasonable value of the impeller parameter of the degasser,in this paper,the influence of parameters such as the number of impeller blades,the bending form of blades,the diameter of impeller and the rotational speed of impeller are analyzed.The results show that: The increase of the number of blades can make the distribution of velocity field and pressure field more uniform;The backward-bending blade can reduce the area of backflow and vortex in the flow field and prevent the occurrence of cavitation;The velocity of the fluid near the blade inlet increases with the increase of diameter of the impeller,while the pressure near the blade inlet decreases,and it will help to form a greater pressure difference with the outside,then the fluid is sucked into the impeller area;The speed of fluid in the rotary area increases and the blade inlet pressure decreases with the increase of rotational speed of impeller,and the backflow and vortex area near the inner wall of diffuser increases,when the rotational speed is less than 1500 r/min,the pressure difference formed between blade inlet and the outside is too small,which is not conducive to the impeller to suck the fluid in,and when the rotational speed is higher than 2000 r/min,the inlet pressure of the blade is too low,thus cavitation phenomenon occurs.